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      <time datetime="2015-12-26 00:00:00 +0800" itemprop="datePublished" class="post-meta__date date">2015-12-26</time> &#8226; <span class="post-meta__tags tags">自定义View,太极</span> &#8226; View <span id="busuanzi_value_page_pv"></span> times.
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    <h1 class="post-title">二十多行代码画太极</h1>
  </header>

  <section class="post">
    <p>一个然并卵的自定义View实例，觉得很有趣就做了一个试试，效果看起来貌似还是挺不错的，代码也非常简单。</p>

<p>如果想系统的学习自定义View，可以参考: <a href="http://www.gcssloop.com/customview/CustomViewIndex">安卓自定义View教程目录</a></p>

<h2 id="完成效果图">完成效果图</h2>

<p><img src="http://gcsblog.oss-cn-shanghai.aliyuncs.com/blog/2019-04-29-072006.gif?gcssloop" alt="太极" /></p>

<h2 id="技术基础">技术基础</h2>

<p>这一篇内容主要设计到安卓中的2D绘图部分，主要用到的是Canvas，使用到的主要技术可以参考下面两篇文章：</p>

<ul>
  <li><a href="http://www.gcssloop.com/customview/Canvas_BasicGraphics">安卓自定义View进阶 - Canvas之绘制图形</a></li>
  <li><a href="http://www.gcssloop.com/customview/Canvas_Convert">安卓自定义View进阶 - Canvas之画布操作</a></li>
</ul>

<h2 id="绘制太极">绘制太极</h2>

<h3 id="1定义画笔">1.定义画笔</h3>

<p>由于太极图像由黑白两色构成，为了方便就定义了两个画笔，分别绘制黑色和白色。</p>

<div class="language-java highlighter-rouge"><pre class="highlight"><code><span class="kd">private</span> <span class="n">Paint</span> <span class="n">whitePaint</span><span class="o">;</span>   <span class="c1">//白色画笔</span>
<span class="kd">private</span> <span class="n">Paint</span> <span class="n">blackPaing</span><span class="o">;</span>   <span class="c1">//黑色画笔</span>
<span class="c1">//初始化画笔函数</span>
<span class="kd">private</span> <span class="kt">void</span> <span class="nf">initPaints</span><span class="o">()</span> <span class="o">{</span>
    <span class="n">whitePaint</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Paint</span><span class="o">();</span>
    <span class="n">whitePaint</span><span class="o">.</span><span class="na">setAntiAlias</span><span class="o">(</span><span class="kc">true</span><span class="o">);</span>
    <span class="n">whitePaint</span><span class="o">.</span><span class="na">setColor</span><span class="o">(</span><span class="n">Color</span><span class="o">.</span><span class="na">WHITE</span><span class="o">);</span>

    <span class="n">blackPaing</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Paint</span><span class="o">(</span><span class="n">whitePaint</span><span class="o">);</span>
    <span class="n">blackPaing</span><span class="o">.</span><span class="na">setColor</span><span class="o">(</span><span class="n">Color</span><span class="o">.</span><span class="na">BLACK</span><span class="o">);</span>
<span class="o">}</span>
</code></pre>
</div>

<h3 id="2在构造函数中初始化画笔">2.在构造函数中初始化画笔</h3>

<div class="language-java highlighter-rouge"><pre class="highlight"><code><span class="kd">public</span> <span class="nf">TaiJi</span><span class="o">(</span><span class="n">Context</span> <span class="n">context</span><span class="o">)</span> <span class="o">{</span>
    <span class="k">this</span><span class="o">(</span><span class="n">context</span><span class="o">,</span> <span class="kc">null</span><span class="o">);</span>
<span class="o">}</span>

<span class="kd">public</span> <span class="nf">TaiJi</span><span class="o">(</span><span class="n">Context</span> <span class="n">context</span><span class="o">,</span> <span class="n">AttributeSet</span> <span class="n">attrs</span><span class="o">)</span> <span class="o">{</span>
    <span class="k">this</span><span class="o">(</span><span class="n">context</span><span class="o">,</span> <span class="n">attrs</span><span class="o">,</span> <span class="mi">0</span><span class="o">);</span>
<span class="o">}</span>

<span class="kd">public</span> <span class="nf">TaiJi</span><span class="o">(</span><span class="n">Context</span> <span class="n">context</span><span class="o">,</span> <span class="n">AttributeSet</span> <span class="n">attrs</span><span class="o">,</span> <span class="kt">int</span> <span class="n">defStyleAttr</span><span class="o">)</span> <span class="o">{</span>
    <span class="kd">super</span><span class="o">(</span><span class="n">context</span><span class="o">,</span> <span class="n">attrs</span><span class="o">,</span> <span class="n">defStyleAttr</span><span class="o">);</span>
    <span class="n">initPaints</span><span class="o">();</span>
<span class="o">}</span>
</code></pre>
</div>

<h3 id="3在ondraw中使用canvas绘制内容">3.在onDraw中使用Canvas绘制内容</h3>

<h4 id="31-确定画布大小">3.1 确定画布大小</h4>

<div class="language-java highlighter-rouge"><pre class="highlight"><code><span class="kt">int</span> <span class="n">width</span> <span class="o">=</span> <span class="n">canvas</span><span class="o">.</span><span class="na">getWidth</span><span class="o">();</span>                          <span class="c1">//画布宽度</span>
<span class="kt">int</span> <span class="n">height</span> <span class="o">=</span> <span class="n">canvas</span><span class="o">.</span><span class="na">getHeight</span><span class="o">();</span>                        <span class="c1">//画布高度</span>
</code></pre>
</div>

<h4 id="32-将canvas坐标原点移动到画布中心">3.2 将Canvas坐标原点移动到画布中心</h4>

<div class="language-java highlighter-rouge"><pre class="highlight"><code><span class="n">canvas</span><span class="o">.</span><span class="na">translate</span><span class="o">(</span><span class="n">centerPoint</span><span class="o">.</span><span class="na">x</span><span class="o">,</span> <span class="n">centerPoint</span><span class="o">.</span><span class="na">y</span><span class="o">);</span>         <span class="c1">//将画布移动到中心</span>
</code></pre>
</div>

<h4 id="33-绘制背景色">3.3 绘制背景色</h4>

<div class="language-java highlighter-rouge"><pre class="highlight"><code><span class="n">canvas</span><span class="o">.</span><span class="na">drawColor</span><span class="o">(</span><span class="n">Color</span><span class="o">.</span><span class="na">GRAY</span><span class="o">);</span>                           <span class="c1">//绘制背景色</span>
</code></pre>
</div>

<h4 id="34-确定太极的半径大小并绘制两个半圆">3.4 确定太极的半径大小并绘制两个半圆</h4>

<div class="language-java highlighter-rouge"><pre class="highlight"><code><span class="c1">//绘制两个半圆</span>
<span class="kt">int</span> <span class="n">radius</span> <span class="o">=</span> <span class="n">Math</span><span class="o">.</span><span class="na">min</span><span class="o">(</span><span class="n">width</span><span class="o">,</span> <span class="n">height</span><span class="o">)</span> <span class="o">/</span> <span class="mi">2</span> <span class="o">-</span> <span class="mi">100</span><span class="o">;</span>             <span class="c1">//太极半径</span>
<span class="n">RectF</span> <span class="n">rect</span> <span class="o">=</span> <span class="k">new</span> <span class="n">RectF</span><span class="o">(-</span><span class="n">radius</span><span class="o">,</span> <span class="o">-</span><span class="n">radius</span><span class="o">,</span> <span class="n">radius</span><span class="o">,</span> <span class="n">radius</span><span class="o">);</span>   <span class="c1">//绘制区域</span>
<span class="n">canvas</span><span class="o">.</span><span class="na">drawArc</span><span class="o">(</span><span class="n">rect</span><span class="o">,</span> <span class="mi">90</span><span class="o">,</span> <span class="mi">180</span><span class="o">,</span> <span class="kc">true</span><span class="o">,</span> <span class="n">blackPaing</span><span class="o">);</span>            <span class="c1">//绘制黑色半圆</span>
<span class="n">canvas</span><span class="o">.</span><span class="na">drawArc</span><span class="o">(</span><span class="n">rect</span><span class="o">,</span> <span class="o">-</span><span class="mi">90</span><span class="o">,</span> <span class="mi">180</span><span class="o">,</span> <span class="kc">true</span><span class="o">,</span> <span class="n">whitePaint</span><span class="o">);</span>           <span class="c1">//绘制白色半圆</span>
</code></pre>
</div>

<p><img src="http://gcsblog.oss-cn-shanghai.aliyuncs.com/blog/2019-04-29-072008.jpg?gcssloop" alt="" /></p>

<p>在这里简单解释一下drawArc绘制圆弧方法几个参数的意义。</p>

<table>
  <thead>
    <tr>
      <th>参数</th>
      <th>作用</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <td>RectF oval</td>
      <td>绘制的区域（是一个矩形）</td>
    </tr>
    <tr>
      <td>float startAngle</td>
      <td>开始角度</td>
    </tr>
    <tr>
      <td>float sweepAngle</td>
      <td>扫过角度</td>
    </tr>
    <tr>
      <td>boolean useCenter</td>
      <td>是否使用中心</td>
    </tr>
    <tr>
      <td>Paint paint</td>
      <td>画笔</td>
    </tr>
  </tbody>
</table>

<p>另外，由于移动设备屏幕的坐标系和我们在数学中常用的坐标系稍微有点区别，需要注意一下。
在移动设备中一般定义左上角为坐标零点，x轴坐标向右增大，y轴坐标向下增大。而在数学坐标系中一般定义y轴坐标向上为增大方向，所以两者y轴刚好是反向的。</p>

<p>更多可参考：</p>

<ul>
  <li><a href="http://www.gcssloop.com/customview/CoordinateSystem/">安卓自定义View基础 - 坐标系</a></li>
  <li><a href="http://www.gcssloop.com/customview/Canvas_BasicGraphics/">安卓自定义View进阶 - Canvas之绘制图形</a></li>
</ul>

<h4 id="35-绘制两个小圆">3.5 绘制两个小圆</h4>

<div class="language-java highlighter-rouge"><pre class="highlight"><code><span class="c1">//绘制两个小圆</span>
<span class="kt">int</span> <span class="n">smallRadius</span> <span class="o">=</span> <span class="n">radius</span> <span class="o">/</span> <span class="mi">2</span><span class="o">;</span>	<span class="c1">//小圆半径为大圆的一半</span>
<span class="n">canvas</span><span class="o">.</span><span class="na">drawCircle</span><span class="o">(</span><span class="mi">0</span><span class="o">,</span> <span class="o">-</span><span class="n">smallRadius</span><span class="o">,</span> <span class="n">smallRadius</span><span class="o">,</span> <span class="n">blackPaing</span><span class="o">);</span>
<span class="n">canvas</span><span class="o">.</span><span class="na">drawCircle</span><span class="o">(</span><span class="mi">0</span><span class="o">,</span> <span class="n">smallRadius</span><span class="o">,</span> <span class="n">smallRadius</span><span class="o">,</span> <span class="n">whitePaint</span><span class="o">);</span>
</code></pre>
</div>
<p><img src="http://gcsblog.oss-cn-shanghai.aliyuncs.com/blog/2019-04-29-072009.jpg?gcssloop" alt="" /></p>

<h4 id="36-绘制鱼眼">3.6 绘制鱼眼</h4>

<div class="language-java highlighter-rouge"><pre class="highlight"><code><span class="c1">//绘制鱼眼（两个更小的圆）</span>
<span class="n">canvas</span><span class="o">.</span><span class="na">drawCircle</span><span class="o">(</span><span class="mi">0</span><span class="o">,</span> <span class="o">-</span><span class="n">smallRadius</span><span class="o">,</span> <span class="n">smallRadius</span> <span class="o">/</span> <span class="mi">4</span><span class="o">,</span> <span class="n">whitePaint</span><span class="o">);</span>
<span class="n">canvas</span><span class="o">.</span><span class="na">drawCircle</span><span class="o">(</span><span class="mi">0</span><span class="o">,</span> <span class="n">smallRadius</span><span class="o">,</span> <span class="n">smallRadius</span> <span class="o">/</span> <span class="mi">4</span><span class="o">,</span> <span class="n">blackPaing</span><span class="o">);</span>
</code></pre>
</div>
<p><img src="http://gcsblog.oss-cn-shanghai.aliyuncs.com/blog/2019-04-29-072010.jpg?gcssloop" alt="" /></p>

<h3 id="4让太极旋转起来">4.让太极旋转起来</h3>

<h4 id="41-设置旋转角度变量并提供外部访问接口">4.1 设置旋转角度变量，并提供外部访问接口</h4>

<div class="language-java highlighter-rouge"><pre class="highlight"><code><span class="kd">private</span> <span class="kt">float</span> <span class="n">degrees</span> <span class="o">=</span> <span class="mi">0</span><span class="o">;</span>          <span class="c1">//旋转角度</span>
<span class="kd">public</span> <span class="kt">void</span> <span class="nf">setRotate</span><span class="o">(</span><span class="kt">float</span> <span class="n">degrees</span><span class="o">)</span> <span class="o">{</span>
	<span class="k">this</span><span class="o">.</span><span class="na">degrees</span> <span class="o">=</span> <span class="n">degrees</span><span class="o">;</span>
	<span class="n">invalidate</span><span class="o">();</span>                   <span class="c1">//重绘界面</span>
<span class="o">}</span>
</code></pre>
</div>

<h4 id="42-在实际绘制之前调用旋转函数">4.2 在实际绘制之前调用旋转函数</h4>

<div class="language-java highlighter-rouge"><pre class="highlight"><code><span class="c1">//在绘制完背景色后调用即可</span>
<span class="n">canvas</span><span class="o">.</span><span class="na">rotate</span><span class="o">(</span><span class="n">degrees</span><span class="o">);</span>
</code></pre>
</div>

<h4 id="43-不断改变旋转角度">4.3 不断改变旋转角度</h4>

<div class="language-java highlighter-rouge"><pre class="highlight"><code><span class="nd">@Override</span>
<span class="kd">protected</span> <span class="kt">void</span> <span class="nf">onCreate</span><span class="o">(</span><span class="n">Bundle</span> <span class="n">savedInstanceState</span><span class="o">)</span> <span class="o">{</span>
	<span class="kd">super</span><span class="o">.</span><span class="na">onCreate</span><span class="o">(</span><span class="n">savedInstanceState</span><span class="o">);</span>
    <span class="kd">final</span> <span class="n">TaiJi</span> <span class="n">taiJi</span> <span class="o">=</span> <span class="k">new</span> <span class="n">TaiJi</span><span class="o">(</span><span class="k">this</span><span class="o">);</span>
    <span class="n">setContentView</span><span class="o">(</span><span class="n">taiJi</span><span class="o">);</span>
    <span class="kd">final</span> <span class="n">Handler</span> <span class="n">handler</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Handler</span><span class="o">()</span> <span class="o">{</span>
        <span class="kd">private</span> <span class="kt">float</span> <span class="n">degrees</span> <span class="o">=</span> <span class="mi">0</span><span class="o">;</span>
        <span class="nd">@Override</span>
        <span class="kd">public</span> <span class="kt">void</span> <span class="nf">handleMessage</span><span class="o">(</span><span class="n">Message</span> <span class="n">msg</span><span class="o">)</span> <span class="o">{</span>
            <span class="kd">super</span><span class="o">.</span><span class="na">handleMessage</span><span class="o">(</span><span class="n">msg</span><span class="o">);</span>
            <span class="n">taiJi</span><span class="o">.</span><span class="na">setRotate</span><span class="o">(</span><span class="n">degrees</span> <span class="o">+=</span> <span class="mi">5</span><span class="o">);</span>
            <span class="k">this</span><span class="o">.</span><span class="na">sendEmptyMessageDelayed</span><span class="o">(</span><span class="mi">0</span><span class="o">,</span> <span class="mi">80</span><span class="o">);</span>
        <span class="o">}</span>
    <span class="o">};</span>

    <span class="n">handler</span><span class="o">.</span><span class="na">sendEmptyMessageDelayed</span><span class="o">(</span><span class="mi">0</span><span class="o">,</span> <span class="mi">20</span><span class="o">);</span>
<span class="o">}</span>
</code></pre>
</div>

<p><img src="http://gcsblog.oss-cn-shanghai.aliyuncs.com/blog/2019-04-29-072006.gif?gcssloop" alt="太极" /></p>

<h3 id="5完整代码">5.完整代码</h3>

<div class="language-java highlighter-rouge"><pre class="highlight"><code><span class="kd">public</span> <span class="kd">class</span> <span class="nc">TaiJi</span> <span class="kd">extends</span> <span class="n">View</span> <span class="o">{</span>
    <span class="kd">private</span> <span class="n">Paint</span> <span class="n">whitePaint</span><span class="o">;</span>   <span class="c1">//白色画笔</span>
    <span class="kd">private</span> <span class="n">Paint</span> <span class="n">blackPaing</span><span class="o">;</span>   <span class="c1">//黑色画笔</span>

    <span class="kd">public</span> <span class="nf">TaiJi</span><span class="o">(</span><span class="n">Context</span> <span class="n">context</span><span class="o">)</span> <span class="o">{</span>
        <span class="k">this</span><span class="o">(</span><span class="n">context</span><span class="o">,</span> <span class="kc">null</span><span class="o">);</span>
    <span class="o">}</span>

    <span class="kd">public</span> <span class="nf">TaiJi</span><span class="o">(</span><span class="n">Context</span> <span class="n">context</span><span class="o">,</span> <span class="n">AttributeSet</span> <span class="n">attrs</span><span class="o">)</span> <span class="o">{</span>
        <span class="k">this</span><span class="o">(</span><span class="n">context</span><span class="o">,</span> <span class="n">attrs</span><span class="o">,</span> <span class="mi">0</span><span class="o">);</span>
    <span class="o">}</span>

    <span class="kd">public</span> <span class="nf">TaiJi</span><span class="o">(</span><span class="n">Context</span> <span class="n">context</span><span class="o">,</span> <span class="n">AttributeSet</span> <span class="n">attrs</span><span class="o">,</span> <span class="kt">int</span> <span class="n">defStyleAttr</span><span class="o">)</span> <span class="o">{</span>
        <span class="kd">super</span><span class="o">(</span><span class="n">context</span><span class="o">,</span> <span class="n">attrs</span><span class="o">,</span> <span class="n">defStyleAttr</span><span class="o">);</span>

        <span class="n">initPaints</span><span class="o">();</span>
    <span class="o">}</span>

    <span class="c1">//初始化画笔函数</span>
    <span class="kd">private</span> <span class="kt">void</span> <span class="nf">initPaints</span><span class="o">()</span> <span class="o">{</span>
        <span class="n">whitePaint</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Paint</span><span class="o">();</span>
        <span class="n">whitePaint</span><span class="o">.</span><span class="na">setAntiAlias</span><span class="o">(</span><span class="kc">true</span><span class="o">);</span>
        <span class="n">whitePaint</span><span class="o">.</span><span class="na">setColor</span><span class="o">(</span><span class="n">Color</span><span class="o">.</span><span class="na">WHITE</span><span class="o">);</span>

        <span class="n">blackPaing</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Paint</span><span class="o">(</span><span class="n">whitePaint</span><span class="o">);</span>
        <span class="n">blackPaing</span><span class="o">.</span><span class="na">setColor</span><span class="o">(</span><span class="n">Color</span><span class="o">.</span><span class="na">BLACK</span><span class="o">);</span>
    <span class="o">}</span>


    <span class="nd">@Override</span>
    <span class="kd">protected</span> <span class="kt">void</span> <span class="nf">onDraw</span><span class="o">(</span><span class="n">Canvas</span> <span class="n">canvas</span><span class="o">)</span> <span class="o">{</span>
        <span class="kt">int</span> <span class="n">width</span> <span class="o">=</span> <span class="n">canvas</span><span class="o">.</span><span class="na">getWidth</span><span class="o">();</span>          <span class="c1">//画布宽度</span>
        <span class="kt">int</span> <span class="n">height</span> <span class="o">=</span> <span class="n">canvas</span><span class="o">.</span><span class="na">getHeight</span><span class="o">();</span>        <span class="c1">//画布高度</span>

        <span class="n">canvas</span><span class="o">.</span><span class="na">translate</span><span class="o">(</span><span class="n">width</span><span class="o">/</span><span class="mi">2</span><span class="o">,</span> <span class="n">height</span><span class="o">/</span><span class="mi">2</span><span class="o">);</span>    <span class="c1">// 移动坐标原点到画布中心</span>

        <span class="n">canvas</span><span class="o">.</span><span class="na">drawColor</span><span class="o">(</span><span class="n">Color</span><span class="o">.</span><span class="na">GRAY</span><span class="o">);</span>           <span class="c1">//绘制背景色</span>
        <span class="n">canvas</span><span class="o">.</span><span class="na">rotate</span><span class="o">(</span><span class="n">degrees</span><span class="o">);</span>                 <span class="c1">//旋转画布</span>

        <span class="c1">//绘制两个半圆</span>
        <span class="kt">int</span> <span class="n">radius</span> <span class="o">=</span> <span class="n">Math</span><span class="o">.</span><span class="na">min</span><span class="o">(</span><span class="n">width</span><span class="o">,</span> <span class="n">height</span><span class="o">)</span> <span class="o">/</span> <span class="mi">2</span> <span class="o">-</span> <span class="mi">100</span><span class="o">;</span>        		<span class="c1">//太极半径</span>
        <span class="n">RectF</span> <span class="n">rect</span> <span class="o">=</span> <span class="k">new</span> <span class="n">RectF</span><span class="o">(-</span><span class="n">radius</span><span class="o">,</span> <span class="o">-</span><span class="n">radius</span><span class="o">,</span> <span class="n">radius</span><span class="o">,</span> <span class="n">radius</span><span class="o">);</span>   <span class="c1">//绘制区域</span>
        <span class="n">canvas</span><span class="o">.</span><span class="na">drawArc</span><span class="o">(</span><span class="n">rect</span><span class="o">,</span> <span class="mi">90</span><span class="o">,</span> <span class="mi">180</span><span class="o">,</span> <span class="kc">true</span><span class="o">,</span> <span class="n">blackPaing</span><span class="o">);</span>            <span class="c1">//绘制黑色半圆</span>
        <span class="n">canvas</span><span class="o">.</span><span class="na">drawArc</span><span class="o">(</span><span class="n">rect</span><span class="o">,</span> <span class="o">-</span><span class="mi">90</span><span class="o">,</span> <span class="mi">180</span><span class="o">,</span> <span class="kc">true</span><span class="o">,</span> <span class="n">whitePaint</span><span class="o">);</span>           <span class="c1">//绘制白色半圆</span>

        <span class="c1">//绘制两个小圆</span>
        <span class="kt">int</span> <span class="n">smallRadius</span> <span class="o">=</span> <span class="n">radius</span> <span class="o">/</span> <span class="mi">2</span><span class="o">;</span>	                            <span class="c1">//小圆半径为大圆的一半</span>
        <span class="n">canvas</span><span class="o">.</span><span class="na">drawCircle</span><span class="o">(</span><span class="mi">0</span><span class="o">,</span> <span class="o">-</span><span class="n">smallRadius</span><span class="o">,</span> <span class="n">smallRadius</span><span class="o">,</span> <span class="n">blackPaing</span><span class="o">);</span>
        <span class="n">canvas</span><span class="o">.</span><span class="na">drawCircle</span><span class="o">(</span><span class="mi">0</span><span class="o">,</span> <span class="n">smallRadius</span><span class="o">,</span> <span class="n">smallRadius</span><span class="o">,</span> <span class="n">whitePaint</span><span class="o">);</span>

        <span class="c1">//绘制鱼眼（两个更小的圆）</span>
        <span class="n">canvas</span><span class="o">.</span><span class="na">drawCircle</span><span class="o">(</span><span class="mi">0</span><span class="o">,</span> <span class="o">-</span><span class="n">smallRadius</span><span class="o">,</span> <span class="n">smallRadius</span> <span class="o">/</span> <span class="mi">4</span><span class="o">,</span> <span class="n">whitePaint</span><span class="o">);</span>
        <span class="n">canvas</span><span class="o">.</span><span class="na">drawCircle</span><span class="o">(</span><span class="mi">0</span><span class="o">,</span> <span class="n">smallRadius</span><span class="o">,</span> <span class="n">smallRadius</span> <span class="o">/</span> <span class="mi">4</span><span class="o">,</span> <span class="n">blackPaing</span><span class="o">);</span>

    <span class="o">}</span>

    <span class="kd">private</span> <span class="kt">float</span> <span class="n">degrees</span> <span class="o">=</span> <span class="mi">0</span><span class="o">;</span>                  <span class="c1">//旋转角度</span>
    <span class="kd">public</span> <span class="kt">void</span> <span class="nf">setRotate</span><span class="o">(</span><span class="kt">float</span> <span class="n">degrees</span><span class="o">)</span> <span class="o">{</span>
        <span class="k">this</span><span class="o">.</span><span class="na">degrees</span> <span class="o">=</span> <span class="n">degrees</span><span class="o">;</span>
        <span class="n">invalidate</span><span class="o">();</span>                           <span class="c1">//重绘界面</span>
    <span class="o">}</span>
<span class="o">}</span>
</code></pre>
</div>

<h2 id="结语">结语</h2>

<p>虽然写了这么长，但核心代码不过二十几行，其实还是挺简单的，一个没什么用但很中国特色的自定义View。</p>

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